Charge Injection into Organic Crystals: Influence of Electrodes on Dark‐ and Photoconductivity

Studies have been made of dark and photoconductivity in thin anthracene single crystals using a Ce4+ solution as one electrode and a 1MNaCl solution as the other electrode. It was found that the Ce4+ electrode was capable of injecting holes into anthracene in the dark, the saturation current at 15 000 v/cm being about 1 μa/cm2. This current was observed when the Ce4+ electrode was at a positive potential. With the same polarity, it was found that there was practically no increase in the saturation current upon illumination of the crystal with 3650 or 4300 A light; at low voltages there was a distinct photoeffect which was attributed to the emptying of polarization producing traps, thus increasing the internal field. The saturation current was proportional to the sixtenths power of the Ce4+ concentration. At low voltages, the current was very small until a certain voltage, referred to as the onset voltage, was reached, after which the current increased rapidly. The onset voltage was larger for the dark cur...